a. Field of the Invention
This invention relates to a system and method for assessing the effective delivery of ablation therapy to tissue in a body. In particular, the instant invention relates to a system and method for generating and displaying an anatomical map of the tissue and altering a visual characteristic of a portion of the map responsive to an index indicative of the state of ablation therapy.
b. Background Art
Ablation catheters are commonly used to create tissue necrosis in cardiac tissue to correct conditions such as atrial arrhythmia (including, but not limited to, ectopic atrial tachycardia, atrial fibrillation, and atrial flutter). Arrhythmia can create a variety of dangerous conditions including irregular heart rates, loss of synchronous atrioventricular contractions and stasis of blood flow which can lead to a variety of ailments and even death. It is believed that the primary cause of atrial arrhythmia is stray electrical signals within the left or right atrium of the heart. The ablation catheter imparts ablative energy (e.g., radiofrequency energy, cryoablation, lasers, chemicals, high-intensity focused ultrasound, etc.) to cardiac tissue to create a lesion in the cardiac tissue. This lesion disrupts undesirable electrical pathways and thereby limits or prevents stray electrical signals that lead to arrhythmias.
Electroanatomical mapping systems are frequently used during cardiac ablation procedures to generate a visual representation, or anatomical map, of the endocardial surface. This visual representation permits a clinician to track the locations at which ablation therapy is provided and to view the cardiac structure and ablative lesions from a variety of angles. Tracking ablation delivery sites is important because it is often necessary to achieve a contiguous line of necrosis to disrupt undesirable electrical pathways in the tissue—despite the fact that ablation therapy often involves multiple applications of energy at discrete locations.
Conventional anatomical mapping systems used during ablation procedures require the clinician to manually mark treatment regions on the anatomical map. In particular, the clinician provides an input through a conventional input device (e.g., a mouse, keyboard, etc.) to indicate the location or locations on the map at which ablation lesions have been created. This subjective marking occurs despite numerous variabilities including movement of the ablation catheter and heart due to cardiac contractions, ventilation and movements of the clinician and variation in the application of ablative energy resulting, for example, from changing temperature or impedance levels. As a result, there may not be a strong correlation between lesions marked on the anatomical map by the clinician and the effective delivery of ablation therapy. Clinicians therefore frequently engage in repeated and relatively time consuming electrophysiologic mapping procedures to identify locations where additional ablation therapy is required and then provide additional ablative energy to those locations—often in a repeated cycle. These problems are exacerbated for those clinicians who engage in procedures whereby the ablation catheter is intentionally moved (or “dragged”) while generating ablative energy. This type of procedure can help reduce collateral tissue damage and is more time efficient, but increases the odds that manual marking of lesion sites will be inaccurate.
The inventors herein have recognized a need for a system and method for assessing the effective delivery of ablation therapy to tissue in a body that will minimize and/or eliminate one or more of the above-identified deficiencies.